As an electrode catalyst for the anode and cathode of a fuel cell, a technique relating to fine catalyst particles is known, which have a structure that includes a core particle and an outermost layer covering the core particle (so-called “core-shell structure”). For the fine catalyst particles, the cost of the inside of the particles, which hardly participates in a catalyst reaction, can be reduced by the use of a relatively inexpensive material for the core particle.
A method for producing a core-shell catalyst is disclosed in Patent Document 1, in which a copper shell layer is produced by the Cu-underpotential deposition method (Cu-UPD) and then the copper shell layer is substituted with noble metal atoms.